The central hypothesis of this proposal is to test the idea that endothelial LD turnover is critical for metabolic function during normal physiology. A corollary to this hypothesis is that impairments in LD turnover in blood vessels will augment insulin resistant states in models of diet induced insulin resistance. To test this hypothesis, the following Aims are proposed. 1: To elucidate the role of ATGL in regulating LD hydrolysis in EC and inflammation under normal physiological conditions and after diet induced insulin resistance (IR); 2. To interrogate the mechanisms of how EC ATGL regulates vascular function and cellular metabolism; and 3: To decipher the importance of endothelial DGATs on LD synthesis and inflammation. Collectively, we will define for the first time the role of endothelial LD metabolism as it relates to the control of circulating TG and metabolic function, thus potentially uncovering a novel link between endothelial dysfunction and insulin resistance. Moreover, the current model of TG lipolysis by LPL in capillary EC is focused on metabolically active tissues such as heart and skeletal muscle and this cannot explain LD formation in large vessel EC, thus, our experiments will move beyond the dogma and perhaps yield insights into the higher incidence of coronary disease in type 2 diabetic patients with elevated TG levels.